In general, prosthesis is performed when a tooth is damaged or missing due to an oral disease. The prosthesis is to wrap a weak tooth or to restore a missing portion of a tooth. Among the prosthesis methods, a crown bridge is used most generally, which employs the natural tooth positioned on either side of the missing tooth as abutment teeth. As shown in FIG. 1, the crown bridge positions an artificial tooth 12 at a site where a missing tooth was positioned, and prepares a part of the abutment tooth 10, and then securely wraps a crown over the abutment tooth 10.
However, such a crown bridge has disadvantages that it causes a pain to a patient at the time of the preparation (prep) of the tooth, raises a secondary problem such as denaturalization of the dental pulp due to an increase of the prepared amount of the tooth structure of the abutment tooth, and induces exposure of the tooth pulp and hypersensitivity reaction, and the like. Also, since the occlusal surfaces of the abutment teeth are prepared, it is not possible to naturally restore the occlusal surfaces as usual.
Meanwhile, an inlay-type prosthesis as shown in FIG. 2 may be employed to prevent such disadvantages. The inlay prosthesis is to supportingly fit an artificial tooth at a site of a missing tooth, in such a manner that the inlay 22 secured to the side abutment tooth, is press-fit into a recess groove 21 of the artificial tooth 20. After drilling a hole at the abutment tooth (see numeral 10 of FIG. 10) so as to insert protrusions 24 of the inlay 22 thereto, the inlay 22 is inserted into the hole and bonded (cementing) from the upper side so that an insertion portion 27 can be inserted into the recess groove 21 of the artificial tooth 20. The inlay-type prosthesis can be regarded as prosthesis of a type of preparing the abutment tooth in a small amount because there is a small necessity of preparing the abutment tooth 10. However, such a conventional inlay-type prosthesis has a disadvantage that holes should be precisely drilled at the abutment tooth 10 to securely fix the inlay 22 to the abutment tooth 10. In other words, when the precision of the hole drilled at the abutment tooth is reduced, abnormal occlusal occurs thereby causing inconvenience of a patient.
In contrast to the inlay-type prosthesis, as shown in FIG. 3, there has been recently known a press-fitting type prosthesis. The press-fitting type prosthesis is constructed such that a plurality of support portions 33 is provided to wrap the abutment tooth 38, and a male body 37 formed at the support portion 33 is press-fit to a female body 36 of the artificial tooth 35.
The support portion 33 can be provided in plural number, if required, so that it can be easily assembled. However, the conventional press-fitting type prosthesis entails a merit that it has good occlusal and reduces pains of a patient since the abutment tooth 38 is not prepared. Nevertheless, there occurs a disadvantage that the bonding force is reduced because it is of a press-fitting type. Also, the artificial tooth 35 is to be inserted into two abutment teeth in a state where the support portion 33 is attached to the abutment tooth 38 and maintained in the course of the assembly and operation of the prosthesis. Thus, if the male body 37 and the female body 36 are not minutely mated with each other, there could be caused a disadvantage that abnormal occlusal occurs or deformation of the prosthesis occurs when it is used for a long time because it cannot endure the occlusal pressure.